The present invention relates to a zoom lens system and optical apparatus using the same, and more particularly those suitable for video cameras, digital cameras, and cameras using a silver halide film which attempt to stabilize a shot image and to optically correct blurs in the shot image when a zoom lens vibrates and tilts.
An image pick-up system having a long focal length, such as a telephoto lens, is generally so bulky and heavy that it is difficult to stabilize an image for such an image pick-up system. As the image pick-up system vibrates and tilts, a shot image displaces (or blurs) according to the tilt angle and the focal length of the image pick-up system. Thus, various image stabilizing optical systems have conventionally been proposed so as to prevent blurs in short images.
Generally speaking, a diameter and weight in an image stabilizing lens unit are important factors to obtain good image stabilization for large-aperture, telescope type zoom lenses. A large-aperture image stabilizing lens unit would require a large-caliber actuator for driving it, and lens""s heavy weight would result in increased power consumption.
For example, an image stabilizing zoom lens proposed in Japanese Laid-Open Patent Application No. 8-278445 would possibly increase a diameter of image stabilizing lens unit. An image stabilizing zoom lens proposed in Japanese Laid-Open Patent Application No. 9-325269 uses two lenses to reduce image stabilizing lens unit""s weight, and would possibly lead to aberrational fluctuations in stabilizing an image.
A mechanism for vibrating part of lens unit in an image pick-up system and for eliminating blurs in a static shot image generally requires a larger image-blur correction amount, smaller mobile and rotary amounts of a (movable) lens unit to be vibrated for blur corrections, a smaller size for the whole apparatus, and the like.
In addition, where the defocus of the movable lens unit causes much decentering aberration, the decentering aberration defocuses images after blurs are corrected. Therefore, an optical system having the image stabilizing function requires a smaller amount of decentering aberration to be generated when the movable lens unit is moved in a direction orthogonal to the optical axis and made in a decentering state.
Accordingly, it is a primary but exemplified object of the present invention to provide a zoom lens system and an optical apparatus using the same, where the zoom lens system has a large aperture but includes such an image stabilizing system having a lightweight and small-diameter image stabilizing lens unit as provides a good optical performance in stabilizing an image, and maintains the entire apparatus compact.
In order to achieve the above object, a zoom lens system of one aspect according to the present invention includes, in order from an object side, a front lens component including, a plurality of lens units for zooming and focusing, and a rear lens component, as a relay lens unit, for forming an image, wherein the rear lens component including, in order from the object side, a lens unit A of positive refractive power, a lens unit B of negative refractive power movable so as to have a component in a direction perpendicular to an optical axis, and a lens unit C of positive refractive power, the image being displaced as the lens unit B moves so as to have the component in the direction perpendicular to an optical axis. According to this zoom lens system, a beam emitted from the front lens component converges by the lens unit A of relatively large positive refractive power. reduces an axial beam incident upon the lens unit B as an image stabilizing lens unit. and thereby reduces a lens diameter of the lens unit B. The lens unit B has relatively large negative refractive power to increase the image stabilizing sensitivity; while the lens unit C has relatively large positive refractive power and corrects an aberration generated by the lens unit B of relatively large negative refractive power. Thereby, the inventive zoom lens may miniaturize the entire apparatus and maintain a high optical performance throughout the entire zoom range or the entire object length in both reference and image stabilizing states.
An optical apparatus of still another aspect according to the present invention includes the aforementioned zoom lens system and a photoelectric conversion element for receiving an image formed by the zoom lens system.
Other objects and further features of the present invention will become readily apparent from the following description of preferred embodiments with reference to accompanying drawings.